[ampad]

Had a quick question for the forum. I understand that for gases, w = -PΔV, but this is only the case when the gas is pushing against the walls of a container. If gas is in a vessel and a valve is opened to allow the gas to fill another vessel (so it now occupies both), is the gas doing any work?

Thanks,
Ampad

[Borek]

If gas is in a vessel and a valve is opened to allow the gas to fill another vessel (so it now occupies both), is the gas doing any work?

Sure it does, it needs to squeeze whatever was initially in the other vessel.

[Enthalpy]

And if no other object receives all the work, then the outgoing gas acquires speed, which can be exploited in a turbine, or converts to heat, etc.
But applying to such cases thermodynamics, which is a theory of equilibrium, demands caution and precaution.
Many textbooks propose wrong exercises in this context.